Tracing PHP Applications

Compatibilty Requirements

For a full list of supported libraries and language versions, visit the Compatibility Requirements page.

Installation and Getting Started

If you already have a Datadog account you can find step-by-step instructions in our in-app guides for either host-based or container-based set ups.

For descriptions of terminology used in APM, take a look at the official documentation.

For details about open-source contributions to the PHP tracer, refer to the contributing guide.

Setup the Datadog Agent

The PHP APM tracer sends trace data through the Datadog Agent.

Install and configure the Datadog Agent. See the additional documentation for tracing Docker applications or Kubernetes applications.

For Agent version 7.18.0 and above, APM is enabled by default for all environments without further action. If you are running an older version of the agent, make sure the Agent has APM enabled.

Install the extension

Install the PHP extension using one of the precompiled packages for supported distributions.

Once downloaded, install the package with one of the commands below.

# using RPM package (RHEL/Centos 6+, Fedora 20+)
rpm -ivh datadog-php-tracer.rpm

# using DEB package (Debian Jessie+ , Ubuntu 14.04+ on supported PHP versions)
dpkg -i datadog-php-tracer.deb

# using APK package (Alpine)
apk add datadog-php-tracer.apk --allow-untrusted

The extension will be installed for the default PHP version. To install the extension for a specific PHP version, use the DD_TRACE_PHP_BIN environment variable to set the location of the target PHP binary before installing.

export DD_TRACE_PHP_BIN=$(which php-fpm7)

Restart PHP (PHP-FPM or the Apache SAPI) and then visit a tracing-enabled endpoint of your application. View the APM UI to see the traces.

Note: It might take a few minutes before traces appear in the UI. If traces still do not appear after a few minutes, run the dd-doctor.php diagnostic script from the host machine to help identify any issues.

If you can’t find your distribution, you can manually install the PHP extension.

Automatic Instrumentation

Tracing is automatically enabled by default. Once the extension is installed, ddtrace traces your application and sends traces to the Agent.

Datadog supports all web frameworks out of the box. Automatic instrumentation works by modifying PHP’s runtime to wrap certain functions and methods to trace them. The PHP tracer supports automatic instrumentation for several libraries.

Automatic instrumentation captures:

• Method execution time
• Relevant trace data, such as URL and status response codes for web requests or SQL queries for database access
• Unhandled exceptions, including stacktraces if available
• A total count of traces (e.g., web requests) flowing through the system

Note: If your application does not use Composer nor an autoloader registered with spl_autoload_register(), set the environment variable, DD_TRACE_NO_AUTOLOADER=true, to enable automatic instrumentation.

Change Agent Hostname

Configure your application level tracers to submit traces to a custom Agent hostname:

The PHP tracer automatically looks for and initializes with the ENV variables DD_AGENT_HOST and DD_TRACE_AGENT_PORT.

See tracer configuration for more information on how to set these variables.

Configuration

The PHP tracer can be configured using environment variables.

Note: If you use code auto-instrumentation (the recommended approach) be aware that the instrumenting code is executed before any user code. As a result, the environment variables below must be set at the server level and be available to the PHP runtime before any user code is executed. For example, putenv() and .env files would not work.

Apache

For Apache with php-fpm, use the env directory in your www.conf configuration file to configure the php tracer, for example:

; Example of passing the host environment variable SOME_ENV
; to the PHP process as DD_AGENT_HOST
env[DD_AGENT_HOST] = $SOME_ENV
; Example of passing the value 'my-app' to the PHP
; process as DD_SERVICE
env[DD_SERVICE] = my-app

Alternatively, you can use SetEnv from the server config, virtual host, directory, or .htaccess file.

SetEnv DD_TRACE_DEBUG true

NGINX

For NGINX, use the env directive in the php-fpm’s www.conf file, for example:

; Example of passing the host environment variable SOME_ENV
; to the PHP process as DD_AGENT_HOST
env[DD_AGENT_HOST] = $SOME_ENV
; Example of passing the value 'my-app' to the PHP
; process as DD_SERVICE
env[DD_SERVICE] = my-app

Note: If you have enabled APM for your NGINX server, make sure you have properly configured the opentracing_fastcgi_propagate_context setting for distributed tracing to properly work. See NGINX APM configuration for more details.

PHP CLI server

Set in the command line to start the server.

DD_TRACE_DEBUG=true php -S localhost:8888

Environment Variable Configuration

Integration names

The table below specifies the default service names for each integration. Change the service names with DD_SERVICE_MAPPING.

Use the name when setting integration-specific configuration such as, DD_TRACE_<INTEGRATION>_ANALYTICS_ENABLED, for example: Laravel is DD_TRACE_LARAVEL_ANALYTICS_ENABLED.

Map resource names to normalized URI

For HTTP server and client integrations, the URL is used to form the trace resource name in the format <HTTP_REQUEST_METHOD> <NORMALIZED_URL>, with the query string removed from the URL. This allows better visibility in any custom framework that is not automatically instrumented by normalizing the URLs and grouping together generic endpoints under one resource.

Numeric IDs, UUIDs (with and without dashes), and 32-to-512-bit hexadecimal hashes are automatically replaced with a ? character.

You can turn this functionality OFF using DD_TRACE_URL_AS_RESOURCE_NAMES_ENABLED=false.

Custom URL-To-Resource Mapping

There are a few cases that are not covered by the automatic normalization that is applied.

There are two classes of scenarios that are not covered by automatic normalization:

• The path fragment to normalize has a reproducible patter nand can be present in any part of the url, for example id<number> in the example above. This scenario is covered by the setting DD_TRACE_RESOURCE_URI_FRAGMENT_REGEX below.
• The path fragment can be anything, and the previous path fragment indicates that a value has to be normalized. For example /cities/new-york tells us that new-york has to be normalized as it is the name of a city. This scenario is covered by settings DD_TRACE_RESOURCE_URI_MAPPING_INCOMING and DD_TRACE_RESOURCE_URI_MAPPING_OUTGOING for incoming and outgoing requests respectively.

DD_TRACE_RESOURCE_URI_FRAGMENT_REGEX

This setting is a CSV of regex that are applied to every path fragment independently. For example setting DD_TRACE_RESOURCE_URI_FRAGMENT_REGEX to ^id\d+$ for the first example /using/prefix/id123/for/id would apply the regex to all framents using, prefix, id123, for, and id. The final normalized resorce name would be GET /using/prefix/?/for/id.

Note that multiple regular expressions separated by a comma can be added ^id\d+$,code\d+$ and that the comma character , is not escaped, hence it cannot be used in the regular expression.

DD_TRACE_RESOURCE_URI_MAPPING_INCOMING and DD_TRACE_RESOURCE_URI_MAPPING_OUTGOING

This setting is a CSV of patterns that can contain a wildcard *. For example, adding the pattern cities/* means that everytime the fragment cities is found while analyzing a URL, then the next fragment, if any, will be replaced with ?. Patterns are applied at any depth, so applying the following rule will both normalize /cities/new-york and /nested/cities/new-york in the table above.

Patterns can be applied to a part of a specific fragment. For example path/*-fix would normalize the url /some/path/changing-fix/nested to /some/path/?-fix/nested

Note that DD_TRACE_RESOURCE_URI_MAPPING_INCOMING applies to only incoming requests (for example web frameworks) while DD_TRACE_RESOURCE_URI_MAPPING_OUTGOING only applies to outgoing requests (for example curl and guzzle requests).

Upgrading

To upgrade the PHP tracer, download the latest release and follow the same steps as installing the extension.

Note: If you are using second level caching in OPcache by setting the parameter opcache.file_cache, remove the cache folder.

Removing

To remove the PHP tracer:

1. For php-fpm, stop the php-fpm service, otherwise stop the Apache web server.
2. Unlink files 98-ddtrace.ini and 99-ddtrace-custom.ini from your php configuration folder.
3. For php-fpm, restart php-fpm service, otherwise restart the Apache web server.

Note: If you are using second level caching in OPcache by setting the parameter opcache.file_cache, remove the cache folder.

Further Reading

お役に立つドキュメント、リンクや記事:

PHP monitoring with Datadog APM and distributed tracingBLOG Source codeGITHUB Explore your services, resources and tracesDOCUMENTATION Advanced UsageDOCUMENTATION